The present era has been called the "age of the material's revolution", wherein non-ferrous objects have been increasingly utilized in lieu of conventional iron and steel materials. In this context, the use of ceramic materials has become increasingly prevalent, with the result that ceramics now constitutes a "third material" which ranks in usage next to metals and plastics.
Historically, ceramics have been widely used because of their heat resistance, corrosion resistance, and anti-abrasion properties. Recently, new ceramic materials have been developed which take full advantage of these characteristics. Silicon nitride and silicon carbide, in particular, are the rising stars of these new ceramics and are the object of fierce competition in research and development.
Silicon nitride, with its very high thermal impulse resistance, excellent corrosion resistance, insulating properties as well as its inherent anti-abrasion properties is widely studied for applications in the field of aerospace, electronics, iron and steel, and ocean development. Because of its high temperature durability the material can also be used in ceramic engines.
Although these materials have attracted a great deal of attention, silicon nitride ceramics are thus far industrially available only in the form of powder or lump.
When in the form of a whisker or "whiskery crystal"--a single unit crystal--silicon nitride exhibits much higher mechanical strength than lump crystals of the same material. Thus whisker crystals of silicon nitride are receiving attention as reinforcing additives for obtaining composite materials of high mechanical strength.